Apparatus for preparing semiconductor rods



Dec. 28, 1965 T. RUMMEL APPARATUS FOR PREPARING SEMICONDUCTOR RODS Filed Dec. 6, 1963 SLIDE COUPLING COOLAN OIL United States Patent 3,226,203 APPARATUS FOR PREPARING SEMI- CONDUCTOR RODS Theodor Rummel, Munich, Germany, assignor t0 Siemens & Halske Aktiengesellschaft, Berlin, Germany, a corporation of Germany Filed Dec. 6, 1963, Ser. No. 328,636 Claims priority, application Germany, Dec. 10, 1962, 8 82,779 Claims. (Cl. 23-273) My invention relates to the production of semiconductor rods, and particularly to an apparatus wherein molten semiconductor material, or the semiconductor material which may be separated at high temperatures from a reaction gas, is crystallized in a desired growth direction onto a seed so as to form a semiconductor rod, and is then drawn out of the high temperature range.

A usual method of preparing semiconductor monocrystals consists of drawing a rod out of a semiconductor melt with a seed crystal, preferably a monocrystal of the same semiconductor material. The melt may be held in a crucible or supported between two vertically aligned rods, as in crucible-free zone melting, wherein one rod is progressively melted while the other serves as a seed crystal. Another process consists of holding the melt in the shape of a freely adhering drop on the lower end of a seed crystal and supplying it with new semiconductor material from a reaction gas which is blown against the hot melt, and which upon contact releases its semiconductor constituent. This can also be accomplished with powdered semiconductor material blown against the melt. Still other processes comprise crystallizing a molten drop on a seed crystal by an electrical gas discharge produced between the seed crystal and a counter electrode. Other methods include crucible-free zone melting, especially drawing thin semiconductor rods according to the state of the art.

In such methods withdrawal of the rod from the heated zone presents problems.

An object of my invention is to provide a semiconductor crystallizing apparatus having improved rod withdrawal means.

According to a feature of my invention a semiconductor rod within a process vessel surrounding the formation location thereof, is slidably held for guidance in one direction, and is withdrawable by a device operating on the rod outside of the vessel from its point of origin within the vessel through a cooled sluice or sealing device provided in the vessel wall having several annular elastic sealing members in contact with the rod. Preferably the device operating on the rod constitutes rollers.

According to another feature of our invention the sluice or sealing device through which the rod is guided out of the process vessel is comprised of at least two gas tight or vacuum tight chambers closed to each other as well as to the vessel atmosphere and the outside atmosphere by means of at least one annular sealing member and the semiconductor rod guided out through the sealing member.

These and other features of novelty are pointed out in the claims. Other objects and advantages of the invention will become obvious from the following detailed description when read in light of the accompanying drawing showing a cross section of a device embodying features of the invention.

In the drawing a thin rod is shown as being drawn upwardly in this case. However, even in other processes the vertical arrangement of the rod is used in the interest of obtaining uniformity of crystallization.

In the drawing a quartz processing or reaction vessel 1 encloses a crucible 2 which a high-frequency coil 3 Patented Dec. 28, 1965 heats inductively, and which holds a silicon, germanium or other semiconductor melt 4. Drawn from the melt 4 is a rod 5 which is held in the vicinity of the melt by a guide 6, and driven by a pair of rollers 7 located outside of the process vessel 1 and rotated by a rotor not shown. The guide 6 is located immediately in the vicinity of the melt 4, but sufiiciently far from the melt so as not to be adversely affected thereby. This is a distance of approximately 2 cm. from the border between the solid and liquid phases. Preferably the distance is shortened to several millimeters by using special materials for the parts of guide 6 contacting the rod 5. Such materials for guide 6, which can be shaped as glide or roller drives, are quartz, silicon carbide or high melting-point metals (Mo, W, Ta) coated with quartz or silicon carbide of the best available purity.

Two roller pairs 8 and 8', turned from the rollers 7, have functions and shapes to be described. Between guide 6 and rollers 7 the semiconductor rod 5 is guided outwardly from the vessel 1 through a sluice 9. The latter possesses three chambers 90, 9b, 9c which are sealed by four flat, annular, ring sealers 10a, 10b, 10c and 10d as well as by the rod 5 passing through the inner openings of the sealers.

The ring sealers 10a, 10b, 10c, 10d consist preferably of an elastic material such as rubber, caoutchouc (hard rubber) or silicone rubber having their peripheries tightly locked to the walls of vessel 1 or with intermediate members sealed to the housing. Their centers are stamped out, so as to form center openings of smaller diameters than the rod 5. If a rod diameter change is expected, then center opening size of the sealer rings is less than the smallest expected diameter. Testing of the illustrated apparatus reveals that a sealing ring inner diameter, 5 to 10% less than the diameter of the rod to be passed therethrough, achieves a satisfactory seal. As shown the center openings of rings 10a to 10d are equal to each other and coaxial to permit easy guidance of the rod 5 through the sluice. In operation a seed crystal which is long enough to reach from the melt 4 through the drive rollers 7 to the drive rollers 8 and S, is inserted through the sluice to start the process. Its size is thus sufiicient to lock the process vessel 1 from the ambient space and at the same time to assure the necessary drive.

Both the inner chambers 9a and 9b are then evacuated or rinsed with a stream of inert protecting gas or hydrogen. The upper chamber 90 is filled with fluid cooling means, quiet or circulating, such as water or oil. Supplementary cooling means may also be provided. Cooling means and material for the sealing rings must of course be compatible to prevent deterioration or diverse effects. During operation of the drives the coolant intensity is set to minimize reaction between the chamber sealers 10a to 10:1 and the hot rod 5, or the hot reaction gas at the inside of the process vessel.

The seed is then brought into contact with the melt in the usual manner for forming a monocrystal and withdrawn by the lower drive 7. The latter is adjusted to the desired drawing speed. The upper drive 8' is adjusted to a somewhat faster drawing speed. However, the upper drive 8' is rotated through a slide coupling 12 and due to the lower drive 7 is slowed in its operation. The rod is then separated between both drives by intermittently operating electrical or pyrolytic severing means 11 such as a high-frequency coil, electric are or automatic welding burner which melt through the rod at a location between members 7 and 8. The separation occurs during withdrawal of the rod as it is formed, at intervals determined by the desired rod lengths. The upper drive system 8 then takes over the transport of the separated part of the semiconductor rod to a magazine in which the cut off portion is stacked by means of intermediate glide planes.

While embodiments of the invention have been described in detail it will be obvious to those skilled in the art that the invention may be practiced otherwise without departing from its spirit and scope.

I claim:

1. Apparatus for producing semiconductor rods by causing molten semiconductor material to grow in preferred crystalline orientation on a seed at a locality of high temperature and removing the resulting solidified rod to a locality of lower temperature, comprising a processing vessel, heatable crystal-forming means in said vessel, a guide mounted in said vessel in spaced relation to said crystal-forming means and engageable with the solidified crystal rod being produced to guide the rod for displacement in the axial direction away from said crystal-forming means, a sealing device mounted on the vessel wall in coaxial alignment with said guide and spaced therefrom in said direction, said sealing device having cooling means and a plurality of axially spaced elastic sealing members coaxially surrounding the rod-displacement axis, said sealing members being sealingly contactable with the rod passing through said device to the outside of said vessel, and rod drive means mounted outside said vessel and drivingly engageable with the rod for pulling the longitudinally growing crystal rod through said guide and said sealing device.

2. Apparatus for producing semiconductor rods by causing molten semiconductor material to grow in preferred crystalline orientation on a seed, comprising a processing vessel, heatable crystal-forming means in said vessel, a guide mounted in said vessel above said crystalforming means and engageable with the solidfiied crystal rod being produced to guide the rod for displacement upwardly, a sealing device mounted on the vessel wall in coaxial alignment with said guide and spaced upwardly therefrom, said sealing device having cooling means and a plurality of axially spaced elastic sealing members coaxially surrounding the rod-displacement axis, said sealing members being sealingly contactable with the rod passing through said device to the outside of said vessel, and rod drive means mounted above said vessel and drivingly engageable with the rod for pulling the longitudinally growing crystal rod through said guide and said sealing device.

3. Apparatus for producing semiconductor rods by causing molten semiconductor material to grow in a preferred crystalline orientation on a seed at a locality of high temperature and removing the resulting solidified rod to a locality of lower temperature, comprising a processing vessel, heatable crystal-forming means in said vessel,

a guide mounted in said vessel in spaced relation to said crystal-forming means and engageable with the solidified crystal rod being produced to guide the rod for displacement in the axial direction away from said crystal-forming means, a sealing device mounted on the vessel wall in co-axial alignment with said guide and spaced therefrom in said direction, said sealing device having cooling means and a plurality of axially spaced elastic sealing members coaxially surrounding the rod-displacement axis, said sealing members being sealing contactable with the rod passing through said device to the outside of said vessel, and rod drive means mounted outside said vessel and drivingly engageable with the rod for pulling the longitudinally growing crystal rod through said guide and said sealing device, said drive means including a pair of rollers engaging the rod.

4. Apparatus for producing semiconductor rods by causing molten semiconductor material to grow in preferred crystalling orientation on a seed at a locality of high temperature and removing the resulting solidified rod to a locality of lower temperature, comprising a processing vessel, heatable crystal-forming means in said vessel, a guide mounted in said vessel in spaced relation to said crystal-forming means and engageable with the solidified crystallized rod being produced at a distance of at most 2 cm. from the phase-border between the solid rod and the molten semiconductor to guide the rod for displacement in the axial direction away from said crystal-forming means, a sealing device mounted on the vessel wall in coaxial alignment with said guide and spaced therefrom in said direction, said sealing device having cooling means and a plurality of axially spaced elastic sealing members coaxially surrounding the rod-displacement axis, said sealing members being sealingly contactable with the rod passing through said device to the outside of said vessel, and rod drive means mounted outside said vessel and drivingly engageable with the rod for pulling the longitudinally growing crystal rod through said guide and said sealing device.

5. Apparatus for producing semiconductor rods by causing molten semiconductor material to grow in preferred crystalline orientation on a seed at a locality of high temperature and removing the resulting solidified rod to a locality of lower temperature, comprising a processing vessel, heatable crystal-forming means in said vessel, a guide mounted in said vessel in spaced relation to said crystal-forming means and engageable with the solidified crystal rod being produced to guide the rod for displacement in the axial direction away from said crystalforming means, a sealing device mounted on the vessel wall in coaxial alignment with said guide and spaced therefrom in said direction, said sealing device having cooling means and a plurality of axially spaced elastic sealing members coaxially surrounding the rod-displacement axis, said sealing members being sealingly contactable with the rod passing through said device to the outside of said vessel, and rod drive means mounted outside said vessel and drivingly engageable with the rod for pulling the longitudinally growing crystal rod through said guide and said sealing device, said drive means including a pair of rollers engaging the rod, said sealing members dividing said sealing device into chambers sealed from each other and from the inside and outside of said vessel, said chambers being bounded by said vessel wall and said rod and said sealing members.

6. Apparatus for producing semiconductor rods by causing molten semiconductor material to grow in preferred crystalline orientation on a seed at a locality of high temperature and removing the resulting solidified rod to a locality of lower temperature, comprising a processing vessel, heatable crystal-forming means in said vessel, a guide mounted in said vessel in spaced relation to said crystal-forming means and engageable with the solidified crystal rod being produced to guide the rod for displacement in the axial direction away from said crystal-forming means, a sealing device mounted on the vessel wall in coaxial alignment with said guide and spaced therefrom in said direction, said sealing device having cooling means and a plurality of axially spaced elastic sealing members coaxially surrounding the roddisplacement axis, said sealing members being sealingly contactable with the rod passing through said device to the outside of said vessel, and rod drive means mounted outside said vessel and drivingly engageable with the rod for pulling the longitudinally growing crystal rod through said guide and said sealing device, said drive means including a pair of rollers engaging the rod, said sealing members dividing said sealing device into chambers sealed from each other and from the inside and outside of said vessel, said chambers being bounded by said vessel wall and said rod and said members, one of said chambers being evacuable.

'7. Apparatus for producing semiconductor rods by causing molten semiconductor material to grow in preferred crystalline orientation on a seed at a locality of high temperature and removing the resulting solidified rod to a locality of lower temperature, comprising a processing vessel, heatable crystal-forming means in said vessel, a guide mounted in said vessel in spaced relation to said crystal-forming means and engageable with the solidified crystal rod being produced to guide the rod for displacement in the axial direction away from said crystalforming means, a sealing device mounted on the vessel wall in coaxial alignment with said guide and spaced therefrom in said direction, said sealing device having cooling means and a plurality of axially spaced elastic sealing members coaxially surrounding the rod-displacement axis, said sealing members being sealingly contactable with the rod passing through said device to the outside of said vessel, and rod drive means mounted outside said vessel and drivingly engageable with the rod for pulling the longitudinally growing crystal rod through said guide and said sealing device, said drive means including a pair of rollers engaging the rod, said sealing members dividing said sealing device into chambers sealed from each other and from the inside and outside of said vessel, said chambers being bounded by said vessel wall and said rod and said members, one of said chambers being filled with a fiuid.

3. Apparatus for producing semiconductor rods by causing molten semiconductor material to grow in preferred crystalline orientation on a seed at a locality of high temperature and removing the resulting solidified rod to a locality of lower temperature, comprising a processing vessel, heatable crystal-forming means in said vessel, a guide mounted in said vessel in spaced relation to said crystal-forming means and engageable with the solidified crystal rod being produced to guide the rod for displacement in the axial direction away from said crystalforming means, a sealing device mounted on the vessel wall in coaxial alignment with said guide and spaced therefrom in said direction, said sealing device having cooling means and a plurality of axially spaced elastic sealing members coaxially surrounding the rod-displacement axis, said sealing members being sealingly contactable with the rod passing through said device to the outside of said vessel, and rod drive means mounted outside said vessel and drivingly engageable with the rod for pulling the longitudinally growing crystal rod through said guide and said sealing device, said drive means including a pair of rollers engaging the rod, said sealing members dividing said sealing device into chambers sealed from each other and from the inside and outside of said vessel, said chambers being bounded by said vessel wall and said rod and said members, one of said chambers being filled with a circulating fluid.

9. Apparatus for producing semiconductor rods by causing molten semiconductor material to grow in preferred crystalline orientation on a seed at a locality of high temperature and removing the resulting solidified rod to a locality of lower temperature, comprising a processing vessel, heatable crystal-forming means in said vessel, a guide mounted in said vessel in spaced relation to said crystal-forming means and engageable with the solidified crystal rod being produced to guide the rod for displacement in the axial direction away from said crystalforming means, a sealing device mounted on the vessel wall in coaxial alignment with said guide and spaced therefrom in said direction, said sealing device having cooling means and a plurality of axially spaced elastic sealing members coaxially surrounding the rod-displacement axis, said sealing members being sealingly contactable with the rod passing through said device to the outside of said vessel, and rod drive means mounted outside said vessel and drivingly engageable with the rod for pulling the longitudinally growing crystal rod through said guide and said sealing device, said drive means including two rotary drive sections axially displaced along the rod, the section closer to the vessel operating at the withdrawal speed of the rod, the section remote from the vessel having a slide-coupling and operation at a speed greater than the first section.

10. Apparatus for producing semiconductor rods by causing molten semiconductor material to grow in preferred crystalline orientation on a seed at a locality of high temperature and removing the resulting solidified rod to a locality of lower temperature, comprising a processing vessel, heatable crystal-forming means in said vessel, a guide mounted in said vessel in spaced relation to said crystal-forming means and engageable with the solidified crystal rod being produced to guide the rod for displacement in the axial direction away from said crystalforming means, a sealing device mounted on the vessel wall in coaxial alignment with said guide and spaced therefrom in said direction, said sealing device having cooling means and a plurality of axially spaced elastic sealing members coaxially surrounding the rod-displacement axis, said sealing members being sealingly contactable with the rod passing through said device to the outside of said vessel, and rod drive means mounted outside said vessel and drivingly engageable with the rod for pulling the longitudinally growing crystal rod through said guide and said sealing device, said drive means including two rotary drive sections axially displaced along the rod, the section closer to the vessel operating at the withdrawal speed of the rod, the section remote from the vessel having a slide-coupling and operating at a speed greater than the first section, and severing means between said two sections for separating portions of said rod which can then be drawn away faster by said remote section.

11. Apparatus for producing semiconductor rods by causing molten semiconductor material to grow in preferred crystalline orientation on a seed at a locality of high temperature and removing the resulting solidified rod to a locality of lower temperature, comprising a processing vessel, heatable crystal-forming means in said vessel, a guide mounted in said vessel in spaced relation to said crystal-forming means and engageable with the solidified crystal rod being produced to guide the rod for displacement in the axial direction away from said crystalforming means, a sealing device mounted on the vessel wall in coaxial alignment with said guide and spaced therefrom in said direction, said sealing device having cooling means and a plurality of axially spaced elastic sealing members coaxially surrounding the rod-displacement axis, said sealing members being sealingly contactable with the rod passing through said device to the outside of said vessel, and rod drive means mounted outside said vessel and drivingly engageable with the rod for pulling the longitudinally growing crystal rod through said guide and said sealing device, said drive means including two rotary drive sections axially displaced along the rod, the section closer to the vessel operating at the withdrawal speed of the rod, the section remote from the vessel having a slide-coupling and operating at a speed greater than the first section, and severing means between said two sections for separating portions of said rod which can then be drawn away faster by said remote section, said severing means comprising means to melt the rod along a limited longitudinal distance.

12. Apparatus for producing semiconductor rods by causing molten semiconductor material to grow in preferred crystalline orientation on a seed at a locality of high temperature and removing the resulting solidified rod to a locality of lower temperature, comprising a processing vessel, heatable crystal-forming means in said vessel, a guide mounted in said vessel in spaced relation to said crystal-forming means and engageable with the solidified crystal rod being produced to guide the rod for displacement in the axial direction away from said crystalforming means, a sealing device mounted on the vessel wall in coaxial alignment with said guide and spaced therefrom in said direction, said sealing device having cooling means and a plurality of axially spaced elastic sealing members coaxially surrounding the rod-displacement axis, said sealing members being sealingly contactable with the rod passing through said device to the outside of said vessel, and rod drive means mounted outside said vessel and drivingly engageable with the rod for pulling the longitudinally growing crystal rod through said guide and said sealing device, said sealing members including sealing discs having interior openings whose diameters are smaller than the diameters of the rod.

13. Apparatus for producing semiconductor rods by causing molten semiconductor material to grow in preferred crystalline orientation on a seed at a locality of high temperature and removing the resulting solidified rod to a locality of lower temperature, comprising a processing vessel, heatable crystal-forming means in said vessel, a guide mounted in said vessel in spaced relation to said crystal-forming means and engageable with the solidified crystal rod being produced to guide the rod for displacement in the axial direction away from said crystalforming means, a sealing device mounted on the vessel wall in coaxial alignment with said guide and spaced therefrom in said direction, said sealing device having cooling means and a plurality of axially spaced elastic sealing members coaxially surrounding the rod-displacement axis, said sealing members being sealingly contactable with the rod passing through said device to the outside of said vessel, and rod drive means mounted outside said vessel and drivingly engageable with the rod for pulling the longitudinally growing crystal rod through said guide and said sealing device, said sealing members including silicone rubber sealing discs having interior openings whose diameters are smaller than the diameter of the rod.

14. Apparatus for producing semiconductor rods by causing molten semiconductor material to grow in a preferred crystalline orientation on a seed at a locality of high temperature and removing the resulting solidified rod to a locality of lower temperature, comprising a processing vessel, heatable crystal-forming means in said vessel, a guide mounted in said vessel in spaced relation to said crystal-forming means and engageable with the solidified crystal rod being produced to guide the rod for displacement in the axial direction away from said crystalforming means, a sealing device mounted on the vessel wall in coaxial alignment with said guide and spaced therefrom in said direction, said sealing device having cooling means and a plurality of axially spaced elastic sealing members coaxially surrounding the rod-displacement axis, said sealing members being sealingly contactable with the rod passing through said device to the outside of said vessel, and rod drive means mounted outside said vessel and drivingly engageable with the rod for pulling the longitudinally growing crystal rod through said guide and said sealing device, said sealing members including caoutchouc sealing discs having interior openings whose diameters are smaller than the diameters of said rods.

15. Apparatus for producing semiconductor rods by causing molten semiconductor material to grow in preferred crystalline orientation on a seed at a locality of high temperature and removing the resulting solidified rod to a locality of lower temperature, comprising a processing vessel, heatable crystal-forming means in said vessel, a guide mounted in said vessel in spaced relation to said crystal-forming means and engageable with the solidified crystal rod being produced to guide the rod for displacement in the axial direction away from said crystalforming means, a sealing device mounted on the vessel Wall in coaxial alignment with said guide and spaced therefrom in said direction, said sealing device having cooling means and a plurality of axially space-d elastic sealing members coaxially surrounding the rod-displacement axis, said sealing members being sealingly contactable with the rod passing through said device to the outside of said vessel, and rod drive means mounted outside said vessel and drivingly engageable with the rod for pulling the longitudinally growing crystal rod through said guide and said sealing device, said sealing members including rubber sealing discs having interior openings whose diameters are smaller than the diameters of said said rods.

References Cited by the Examiner UNITED STATES PATENTS 1,514,517 8/1926 Dufty 308S XR 2,711,833 6/1955 Jacobson et al. 2l4l7.4 XR 2,876,147 3/1959 Kniepkamp et a1 23-273 2,963,001 12/1960 Alexander 34-242 XR 3,032,890 5/1962 Barr et a1. 34-242 XR 3,036,392 5/1962 Sieberto 23273 XR 3,060,065 10/1962 Creal 23301 XR NORMAN YUDKOFF, Primary Examiner. 

1. APPARATUS FOR PRODUCING SEMICONDUCTOR RODS BY CAUSING MOLTEN SEMICONDUCTOR MATERIAL TO GROW IN PREFERRED CRYSTALLINE ORIENTATION ON A SEED AT A LOCALITY OF HIGH TEMPERATURE AND REMOVING THE RESULTING SOLIDIFIED ROD TO A LOCALITY LOWER TEMPERATURE, COMPRISING A PROCESSING VESSEL, HEATABLE CRYSAL-FORMING MEANS IN SAID VESSEL, A GUIDE MOUNTED IN SAID VESSEL IN SPACED RELATION TO SAID CRYSTAL-FORMING MEANS AND ENGAGEABLE WITH THE SOLIDIFIED CRYSTAL ROD BEING PRODUCED TO GUIDE THE ROD FOR DISPLACEMENT IN THE AXIAL DIRECTION AWAY FROM SAID CRYSTAL-FORMING MEANS, A SEALING DEVICE MOUNTED ON THE VESSEL WALL IN COAXIAL ALIGNMENT WITH SAID GUIDE AND SPACED THEREFROM IN SAID DIRECTION, SAID SEALING DEVICE HAVING COOLING MEANS AND A PLURALITY OF AXIALLY SPACED ELASTIC SEALING MEMBERS COAXIALLY SURROUNDING THE ROD-DISPLACEMENT AXIS, SAID SEALING MEMBERS BEING SEALINGLY CONTACTABLE WITH THE ROD PASSING THROUGH SAID DEVICE TO THE OUTSIDE OF SAID VESSEL, AND ROD DRIVE MEANS MOUNTED OUTSIDE SIAD VESSEL AND DRIVINGLY ENGAGEABLE WITH THE ROD FOR PULLING THE LONGITUDINALLY GROWING CRYSTAL ROD THROUGH SAID GUIDE AND SAID SEALING DEVICE. 